The present invention relates to a hydroforming system which requires less capital investment to achieve high pressure hydroforming of tubular parts. The present invention accomplishes this effect by replacing the conventional, separate "intensifier" system for providing high internal pressures within the tubular blank to be expanded.
In accordance with the present invention, water is fed under relatively low pressure to the side ram or hydraulic cylinder assemblies which are used to expand the tubular blank. The side ram assemblies utilize the same hydraulic power source to exert the pressures that are required to expand the tube as well as the pressure that is required to force the opposite ends of the tube inwardly to retain the desired wall thickness of the resultant product. Thus, no separate intensifier is required.
In particular, it is an object of the present invention to provide an apparatus for hydroforming a tubular metal blank that comprises a die structure, a hydroforming fluid source, a hydraulically driven tube-end engaging structure, a hydraulically driven pressure intensifying structure, and a single hydraulic power source. The tube-end engaging structure seals opposite ends of the tubular metal blank in said die cavity and is movable to longitudinally compress the tubular metal blank. The tube-end engaging structure receives hydroforming fluid from said hydroforming fluid source and has a hydroforming fluid supplying outlet through which hydroforming fluid can be provided to the tubular metal blank. The hydraulically driven pressure intensifying structure is movable to pressurize the hydroforming fluid provided to the interior of the tubular metal blank and thereby expand a diameter of the blank. A single hydraulic power source provides the hydraulic fluid under pressure to said hydraulically driven pressure intensifying structure in order to move the pressure intensifying structure and thereby pressurize the hydroforming fluid provided to the interior of the tubular metal blank and expand the diameter of the tubular metal blank so that its exterior surface conforms to that of the internal die surface. The single hydraulic power source also provides the hydraulic fluid under pressure to the hydraulically driven tube-end engaging structure to enable the tube-end engaging structure to longitudinally compress the tubular metal blank and cause metal material of the diametrically expanded tubular blank to flow longitudinally inwardly in order to replenish a wall thickness of the diametrically expanded tubular metal blank and maintain the wall thickness thereof within a predetermined range.
The present invention preferably also utilizes the same hydraulic power source to also apply the downward pressure to an upper die structure when the upper die structure is in its lowered position to oppose the internal die cavity pressure during tube pressurization.
Conventional hydroforming utilizes low pressure (e.g., force of gravity) hydroforming fluid feed from a supply tank to supply hydroforming fluid for quick pre-filling of the tube blank after the die cavities have closed on the tube but prior to the axial cylinders engaging and the tube blank into the cavity. It is a further object of the present invention to use the hydroforming fluid from this same tank to supply a relatively smaller amount of water to intensify the pressure within the tubular blank after it is sealed and is ready to be expanded. This smaller amount of water is supplied to a dual function cylinder used for pushing the tube blank into the die cavity as well as intensifying the fluid pressure inside the die cavity from one side of the tool. By replacing the current intensifiers with a dual function cylinder that supplies the hydraulic push to the tube blank and the internal fluid pressure for forming, the overall cost of the equipment is reduced substantially.
In particular, the object is achieved by providing an apparatus for hydroforming a tubular metal blank comprising a die structure, a hydroforming fluid source, a hydraulically driven tube-end engaging structure, and a hydraulically driven pressure intensifying structure. The die structure has an internal die surface defining a die cavity. The die cavity is constructed and arranged to receive the tubular metal blank. The hydroforming fluid source is disposed higher than the die cavity, and is constructed and arranged to provide hydroforming fluid internally to the tubular metal blank under the force of gravity. The hydraulically driven tube-end engaging structure engages and substantially seal opposite ends of the tubular metal blank in the die cavity. The tube-end engaging structure is movable to longitudinally compress the tubular metal blank. The tube-end engaging structure receives hydroforming fluid from the hydroforming fluid source and has a hydroforming fluid supplying outlet through which hydroforming fluid can be provided to an interior of the tubular metal blank. The hydraulically driven pressure intensifying structure is movable in response to hydraulic fluid pressure to pressurize the hydroforming fluid provided to the interior of the tubular metal blank and thereby expand a diameter of the blank until an exterior surface of the tubular metal blank generally conforms to that of the internal die surface. The hydraulically driven tube-end engaging structure is movable in response to hydraulic fluid pressure to enable the tube-end engaging structure to longitudinally compress the tubular metal blank and cause metal material of the diametrically expanded tubular blank to flow longitudinally inwardly in order to replenish a wall thickness of the diametrically expanded tubular metal blank and maintain the wall thickness thereof within a predetermined range.
The resultant system is much less complex, less cumbersome, and less expensive then conventionally known systems.
Other objects and advantages of the present invention will be appreciated from the following detailed description and appended drawings and claims.